When Yang first presented his work with Mills on non-abelian gauge theories, at Princeton, Pauli was there and had strong doubts about the relevance of their work. He was convinced that the vector bosons must remain massless. See for instance the references in this proceeding. Even (the most brillant) scientists are often wrong on "what to do next" in fundamental research.

Where does every medical imaging device come from ?

What do you think Planck would have answered to "What will be the use of you studying the spectrum of heat emitted by a oven ?" ? Yet, without quantum mechanics, it is unlikely that there would be any decent computer, and in fact any decent transistor at all (you know, this small electronical component pretty much everywhere around you).

What do you think Fourier would have answered to the question "What is the use of studying the propagation of heat with undefined mathematical formulae ?" ?

There is no way to justify fundamental research use to society. This is simply too unfair. One could keep making such lists for ever. Without fundamental research there is pretty much no real progress. Understanding what is "out there" lies at the heart of what makes us human.

IMHO, a serious discussion about this does not belong to this thread, but to the philosophy thread.